Sorry... this is going to be the quick and short answer. I'm short on time. ;-) Yes, there are texture sites that only give you the bigger image that you have to right click on and save. Not all of them provide you with and actual download. To use the texture in Bryce the short answer is to go into the Materials Lab and place a marble in column A, next to Diffuse or Ambient to use the textures color, or nest to Bump to use the texture as a bump, etc. You want to import the downloaded texture as an "Image Texture" for the marble(s) you placed in column A (or even columns B,C, or D).